Circuits to control and drive brushless direct current (BLDC) electric motors are known. Such motors might be implemented as multi-phase electric motors having drive signals corresponding to electrical windings of the motor. In some implementations, the control circuit might include or be coupled to one or more sensors, for example, Hall effect sensors or other similar devices, to sense a position and/or rotational speed of the motor. For example, Hall effect sensors might be employed to sense a magnetic field associated with the motor (or an object coupled to the motor, for example a fan or a crankshaft) as it rotates and, thus, determine a position and/or rotational speed.
In some arrangements, the sensed position and/or rotational speed might be employed to determine the drive signals for the electric motor. For example, the control circuit might change or modulate a shape of the drive signals that drive the electric motor, sense a direction of motion of the motor (e.g., forward or reverse), sense “windmilling” conditions where the motor is moving without being driven by the drive signals, or provide a phase advance of the drive signals to align a phase of a back electromotive force of the motor and a phase of the current through the motor.
In some arrangements, the Hall effect sensors might be sensitive to noise and/or generate output glitches, which can, in turn, lead to the drive signals of the motor being inaccurate relative to the state (e.g., position and/or rotational speed) of the motor. Such inaccuracies between the drive signals and the motor state can cause motor slow down and motor shutdown conditions.
In view of the above, it would be desirable to provide electric motor control circuits and associated methods that can more accurately determine the rotational position of the motor.